Many construction and mining operations require off road work machines to haul loads between various locations. One type of work machine that has excellent off road performance is an articulated work machine. The articulated work machine has a front chassis and a rear chassis which are coupled at a hitch. Generally, a cab is mounted on the front chassis and a load carrying receptacle is mounted on the rear chassis. The articulated work machine has an articulated steering mechanism whereby a pair of hydraulic cylinders steer the work machine. In particular, when the left cylinder is extended, the front chassis rotates about the hitch to the right whereas when the right cylinder is extended, the front chassis rotates about the hitch to the left. Articulated work machines generally have an engine mounted on the front chassis that drives a front axle. In addition, a drive shaft and differential cross the hitch to drive one or more rear axles giving the articulated work machine all wheel drive.
Articulated work machines have several advantages over conventional trucks. The articulated steering mechanism gives the articulated work machine a smaller turning radius than a comparatively sized conventional truck. Moreover, the articulated steering mechanism coupled to the all wheel drive gives the articulated work machine enhanced off road performance allowing the articulated work machine to operate on soft ground in conditions where a conventional truck may become bogged down. Thus, the articulated work machine can haul loads in conditions where a conventional truck may become bogged down.
Despite the advantages of the articulated work machine, articulated work machines that have heretofore been designed have several drawbacks. One drawback is that many articulated work machines mount the engine and drivetrain on the front chassis. Mounting the engine on the front chassis causes most of the engine weight be supported by the front axle. This problem is exacerbated in some articulated work machines that mount the engine a substantial distance ahead of the front axle. When such articulated work machines are empty, the engine weight supported by the front axle exceeds the weight of the empty receptacle supported by the rear axle or axles. Certain countries place limits on the maximum axle weight of work machines that are permitted to operate on the roads. Thus, it may be desirable to redistribute the weight of the engine among the axles so that one or two of the axles do not support a substantially disproportionate amount of the weight.
Another drawback associated with mounting the engine on the front chassis of the articulated work machine is that the extended length of the front cab restricts maneuverability of the work machine. Furthermore, the front mounted engine may reduce visibility out of the front of the cab.
Another drawback associated with mounting the engine on the front chassis is that the heat, noise, and vibrations generated by the engine can cause discomfort to the operator. This is especially true in configuration of the articulated work machine where the cab is not air conditioned.
Another drawback associated with mounting the engine on the front chassis is that there is a large number and type of items that must cross the hitch. For configurations with double rear axles, the drive shaft must be large enough to transfer adequate torque to both of the rear axles. Also, hydraulic power must be supplied from an oil pump, generally located near the engine, from the cab assembly to the trailer assembly to a pair of lift cylinders located on the trailer chassis. The lift cylinders are used to raise and lower the load carrying receptacle.
What is needed therefore is an apparatus and method for powering an articulated work machine which overcomes one or more of the above-mentioned drawbacks.